Small profile high wattage horitcultural luminaire
CROSS REFERENCES TO RELATED APPLICATIONS 
     Ser. No. 07/388,215, filed concurrently herewith, and assigned to the assignee hereof, being a design patent application, contains related subject matter. 
     TECHNICAL FIELD 
     This invention relates to luminaires or light fixtures, particularly suited for horticultural uses. 
     BACKGROUND ART 
     Horticultural luminaires normally use high wattage lamps (1000 W HPS) and in prior art arrangements the ballast and starter is mounted close to the lamp for starting purposes. The ballast normally requires a large housing to dissipate the heat and a large cavity is required for the lamp to provide the required light distribution. Fixtures having a width exceeding 20 inches are very common; and it has been found that wide luminaires obstruct daylight which is undesirable for horticultural applications. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the invention to provide a luminaire wherein less obstruction to daylight is encountered. 
     According to the present invention there is Provided a luminaire comprising a housing for containing a lamp in a first compartment and having an open underside; a first plate member defining one end of the first compartment, a socket for the lamp being mounted on one side of the first plate member; a second plate member on the other side of the first plate member and spaced therefrom to form a second compartment; a ballast unit for the lamp in the second compartment and making heat-conductive contact with the housing and a third plate member covering the open underside portion of the second compartment, the third plate member making heat-conductive contact with the ballast unit. 
     According to another aspect there is provided a luminaire housing, a pair of bracket members mounted on top of the luminaire housing, and at least one bolt member adapted to pass through the brackets to lock the luminaire housing in a desired location on a structural I-beam, the bracket members engaging a lip of the I-beam on opposite sides thereof. 
     An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic cross-sectional view of a horticultural luminaire according to the described embodiment. 
     FIG. 2 is a diagrammatic cross-sectional side view of the luminaire of FIG. 1. 
     FIG. 3 is a perspective view of the luminaire of FIG. 1. 
     FIG. 4 is an end view of the luminaire shown in FIG. 3 to illustrate how it may be mounted on a structural I-beam. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring to the figures, a horticultural luminaire housing 2 contains a high wattage (1000 W HPS) lamp 4. The lamp 4 is mounted in a first compartment 6 (FIGS. 2 and 3) while a second compartment 8 is separated from the first compartment 6 by a first partitioning plate member 10. The other extremity of the second compartment 8 is defined by a second identical plate member 12 as can be seen in FIG. 2. A socket 14 for lamp 4 is mounted on one side of plate member 10 as shown in FIG. 2. 
     A ballast unit 16 for lamp 4 is mounted in the second compartment 8 and its top surface makes heat-conductive contact with the ballast unit 16 so as to act as a second heat sink for the ballast unit 16. The plate member 20 also covers a third compartment 22 within housing 2 wherein are located an igniter 24 and a capacitor 26 for lamp 4. The igniter 24 and capacitor 26 are mounted on plate member 12. 
     The housing 2 includes a reflector which comprises two separate extruded sections 28 and 30 as can be seen in FIG. 1. The bottom of each section is fastened at 32 or 34 to the respective extruded side of the housing 2 while the top of each section rests on a respective protrusion 36 or 38 on stepped support member 40 or 42. An alternate position for the top of each section is on respective protrusion 44 or 46, effectively between protrusions 36 and 44 or 38 and 46 (FIG. 1). Thus angular variations in the reflector position are possible to change the photometric distribution. 
     The top member 48 of housing 2 was extruded as a single piece to act as a support. However, the sides 50 and 52 may be made as one piece or each may be extruded in two pieces. This separates the lamp compartment from the ballast compartment to permit each reflector section to swing open and close between different positions dependent on the number of mounting holes provided in the end plate 54. The other end plate 56 encloses the compartment containing the igniter 24 and capacitor 26. As will be appreciated, the provision of a plurality of mounting holes in the end plate 54 is effective to multiply the step positions of the reflector relative to the stepped support members 40 and 42, the number of total positions being determined by the number of additional mounting holes in end plate 54. 
     As will be clear from FIG. 1, the two side extrusions 50 and 52 slide into receiving portions 58 and 60, respectively, of the extruded top member 48. As mentioned above, the ballast unit 16 is mounted in the compartment 8 between the two plate members 10 and 12. It is attached to the extruded top member 48 of the housing 2 so that the top member 48 acts as a heat sink for the ballast unit 16. The plate member 20 covering the bottom of compartment 8 acts as a second heat sink for the ballast unit 16. 
     Additional ventilation of compartment 8 is Provided by natural convection at a rate which can be varied to suit the particular application of the luminaire. Air may be guided to pass through the openings in the end of the ballast compartment 8 and through the lamp compartment to exit at the other end of the luminaire fixture via vents 55. A small elevation of the mounting (say 5°-30°) will permit a wide range of operating and surface temperatures to be permitted and thus have been found to be a particular feature of the embodiment. 
     The described luminaire was constructed to provide a 1000 W unit in a package not exceeding 10 inches in width and 7 inches in height with lengths varying from 24-34 inches depending on the required size for a self-contained unit. This was made possible due to the described heat dissipation arrangement for the unit in combination with the adjustable reflector permitting light distribution control. It will be appreciated that as heat dissipation and photometric distribution are important factors in the design of the described high wattage, small sized luminaire, alternate embodiments were successfully tried and resulted in (a) further reduction of the operating temperature, and (b) multiplying the photometric adjustment range. 
     The reduction of the operating range of the luminaire was achieved by sectioning the extrusions with an overlap to provide air gap separators which reduce or prevent heat conduction between the lamp compartment 6 and the ballast compartment 8. Venting the lamp compartment 6 was found to reduce the temperature even more. The use of forced air circulation provided even further lowering of the temperature where this was desired. 
     In FIGS. 3 and 4, a method of mounting the luminaire on an I-beam type structure is diagrammatically illustrated. The luminaire housing 2 is provided with bracket members 62 and 64 which can be used to mount the luminaire fixture on, for example, a building&#39;s 5 inch structural I-beam 66. The luminaire housing 2 can be maintained in place by the use of two bolt members 68 and 70 with corresponding nuts, which lock the luminaire housing in the desired location and provide quick mounting and adjustability of the luminaire, the bracket members 62 and 64 engaging a lip 72 of the I-beam on opposite sides thereof. Thus ease of installation, positioning and maintenance is achieved. It will be understood that in some situations, only one bolt member may be provided and the electrical receptacle 74 for the lamp may be mounted on the I-beam 66, as shown in FIG. 4, and the electrical cable 76 to lamp 4 may be arranged as shown. 
     From the above, it will be seen that a high wattage luminaire (1000 W HPS) of minimum width and depth has been described for use in horticultural applications and it incorporates the ability to be quickly mounted to an I-beam, variable photometric distribution and a low operating temperature is possible. However, it will be readily apparent to a person skilled in the art that a number of variations and modifications can be made without departing from the true spirit of the invention which will now be pointed out in the appended claims.